1. Field of the Invention
The present invention relates to a system configuration of wireless PBX (private branch exchange), and more particularly to a system configuration of wireless PBX using cordless phones suitable for use within the premises of a building or the like which contains a plurality of various rooms each occupying a specific area.
2. Description of the Prior Art
As radio communication technique has developed in recent years, a system using portable telephones such as cordless phones and car telephones is now of practical use. Workers within the premises of buildings, factories and the like often leave their seats, so that conventional wire telephones may sometimes become useless in giving messages to such persons. Accordingly there are much demands for a system wherein extension telephones within the premises are made cordless, and a user carries a cordless phone with him or her so that telephone communications are allowed wherever he or she is within the premises.
An example of multi-zone cordless phones for such a system on the distributed control basis is shown in a report entitled "SYSTEM CONFIGURATION OF MULTI-ZONE CORDLESS TELEPHONE", National Conference Record, 1986, Communications, The Institute of Electronics and Communication Engineers of Japan, at page 2-256. With the cordless telephone system presented in this document, it can be well anticipated that every person is provided with a portable radio mobile station and wired extension telephones commonly present at an office or the like will eventually disappear.
If each person is provided with a wireless telephone, a particular person can be called easily. However, it becomes very difficult to call an unspecified person in a particular location. The situation of "Calling an unspecified person in a particular location" is, for example, a situation where a certain person present at the meeting in an arbitrary meeting room wishes to ask an unspecified person in the room to do something. In such a situation, the person at the meeting does not known who is present in the room. Therefore, the person at the meeting is forced to call persons who, the person at the meeting considers, will probably be present in the room, on the trial and error base, or carry out other measures.